The electrification of the automobile is presently being vigorously advanced, with research focusing, in particular, on the lithium ion battery. To be of interest to the consumer, batteries for uses in electric cars must ensure a long service life (>10 years). This means that the cell voltage and the energy being released during a discharge should still equal ≥90% of the initial values, even after 10 years. These requirements have yet to be met in the case of so-called high energy materials, such as high energy NCM (LiMO2:Li2MnO3 with m=nickel (Ni), cobalt (Co), manganese (Mn). The HE-NCM so far supplies high start voltages, but manifests a significant loss in the voltage level (voltage fade) during the course of the service life, accompanied by a drop in capacity (capacity fade). For this reason, the in principle highly interesting material HE-NCM is so far unsuitable for commercial exploitation.
To reduce the drop in capacity, the main approach in the literature is to coat the material with, for example, Al2O3, LiAlOx, ZrO2, TiO2, AlPO4, LiPON, etc. (cf. I. Bloom, et al., J. Power Sources 2013), two fundamental approaches for material coatings include: for one, the coating of the starting powder, i.e., of the primary particles and secondary particles, for another, the coating of a finished laminated electrode, in which the cathode material is already processed. The drop in capacity is reduced, but even with these approaches, it continues to remain critical.
To reduce the voltage drop, it is, in principle, conceivable based on the previous findings in the literature to dope redox-inactive elements, such as Mg(II) and Sn(IV), which show no change in the oxidation level and no undesirable migration within the material during the cyclization, and thus stabilize the structure of the material. Dopings of HE-NCM with Mg and Sn is known in the literature. The introduction of redox-inactive elements reduces the drop in voltage and the capacity over time, however, this is associated with an undesirable loss of starting capacity and starting voltage of the cell.
Thus, an object of the present invention is to increase the service life of a lithium ion cell or lithium ion battery, in particular, a HE-NCM lithium ion battery.